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The Autophenakistoscope 



i 



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The Autophenakistoscope 

Written By: Dan Rasmussen 



f TOOLS: 



Computer (1) 

Drafting compass (1) 

Drill and bits (1) 

including 1 A " brad- point bits 

Heat gun (1) 

Multimeter (1) 

Pliers (1) 

Razor saw (1) 

such as X-Acto #X75300 

Sandpaper (1) 

Saw(1) 

to cut the hardboard clean and square. I 
used a chop saw, aka miter saw; you 
could also use a jigsaw with a reverse- 
tooth blade or a band saw. 

Scissors (1) 

such as X-Acto #X7753. Electric 

scissors are optional but handy. 

Screwdrivers (1) 

Sharpie markers (1) 



© PARTS: 



Unwanted CD or DVD (1) 

Power supply (1) 

I used a 1A supply from my junk box. 

Cardboard (1) 
such as mat board 

Hardboard panel (1) 
for the stand and box 

Wood glue or white glue (1) 

Maksing tape (1) 

Adhesive (1) 

Zip ties (1) 

Terminal strip (1) 
Jameco #215011 

Additional knob(1) 

to secure disks to the motor shaft 

Screws (2) 

for mounting the motor. Use parts #309 
and #139 from Du-Bro 
(http://dubro.com/hobby), or try your 
local hardware store. 



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The Autophenakistoscope 



Soldering iron (1) 
Wire cutter/stripper (1) 
Wrenches (1) 
X-Acto knife (1) 



Gearmotor (1) 

I used a 6V DC 488rpm spur gear motor 
containing a Mabuchi #FF-030 motor, 
part #MS-1 6024-030 from BaneBots 
(http.V/banebots . com) , $13. 

Heat-shrink tubing (1) 

Knobs (2) 

to fit the 5 K pots, such as Jameco 

#265009 

resistors (2) 

Switch (1) 
Jameco #16523 

Potentiometer (2) 
Jameco #264402 

Solder (1) 

Hookup wire (1) 
various colors 

Infrared emitter and detector pair (1) 
RadioShack (http://radioshack.com) part 
#276-0142. The ones packaged together 
in a small plastic bag work better than 
the ones in a blister pack (both have the 
same part number). 

LED holder/diffuser lens (1) 

Mouser (http://mouser.com) part #593- 

3000GLO 

LED(1) 

Jameco (http://jameco.com) part 
#183231. This is our strobe: the brighter 
the better. 

Freeduino motor control shield kit for 
Arduino (1) 
NKC Electronics 
(http://nkcelectronics.com) part #ARD- 



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The Autophenakistoscope 



0015. $11 

Headers (1) 

NKC Electronics #ARD-0021. $2 

Arduino Duemilanove (1) 

Maker Shed (http://makershed.com) part 

#MKSP4. $35 

LED holders (2) 
RadioShack #276-079 

Paint (1) 

Foam tape ( 1 ) 
about 12" 



SUMMARY 

Motorize a phenakistoscope, a 19th-century parlor novelty that preceded motion pictures, 
and keep its frames synched to an LED strobe by using a sensor and an Arduino 
microcontroller. 

Invented in 1832 by Joseph Plateau, this device creates a moving picture from a sequence 
of stills arranged on a spinning disk and viewed through strategically cut slits. It's easy to 
see how this invention and others like it evolved into movies and television. 

My 9-year-old daughter and I wanted to make something new with Lego Mindstorms. We had 
a strobe, and we thought of combining it with a spinning disk to create animation. But it was 
difficult attaching the disk to the Lego motor, and we couldn't control the motor and strobe 
speeds precisely enough to get them to match. The project really came together once we 
started using a gearmotor to give the disk a smooth, finely controllable rotation speed. 

With an adjustable-frequency strobe, we experimented with persistence of vision and 
sympathetic frequencies, and produced several interesting visual effects. Finally, using an 
Arduino, a simple C program, and a sensor, we automatically synchronized the strobe with 
the rotating disk. A switch toggles between manual and microcontroller strobe control. 



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The Autophenakistoscope 




Download and print a sample disk image and the templates in the documents area. Print 
the disk image in color, ideally on a laser printer so the colors won't bleed if the disk gets 
wet. 



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The Autophenakistoscope 




• Trim the disk image with scissors but don't cut out the center hole. Glue it to the CD using 
spray adhesive. Let it dry for 30 minutes, then cut out the center hole with an X-Acto knife. 

• Cut out the sync wheel template but not the slits around its perimeter. Adjust a compass to 
the outside radius of the template and use it to draw a circle on the mat board. Then cut 
the circle out of the mat board. 

• Cutting mat board with scissors or an X-Acto knife can be difficult, but electric 
scissors make it easier. The circle doesn't have to be perfect. 

• Tape the sync wheel template onto the mat board disk and use an X-Acto knife to cut the 
slits. Remove the template. 

• Cut the 2 smallest disks from the template out of mat board. The smaller one nests inside 
the CD's hole and the larger one acts like a washer, reinforcing the image disk in back. 




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The Autophenakistoscope 




Cut the paper stand and case templates, and spray-glue them to the hardboard sheet. Let 
the glue dry a minute before sticking the paper down, so it's less permanent. 

Cut out all the pieces following the templates. I started with a chop saw and finished with a 
razor saw. To cut the rectangular indentations (wire channels), use the razor saw to cut 
the sides, then score the top cut with an X-Acto knife and snap it off. Sand all cut edges 
smooth. 

Mark and drill the holes for mounting the motor, IR emitter and sensor, and LED strobe. A 
brad-point bit will make this easier. I should have used (but didn't) snap-in, panel-mount 
LED holders, which mount easily into Vi" holes. 

Glue the pieces together to form the stand and case, using masking tape to hold 
everything together until it dries. Don't glue the front panel cover (that comes later) or the 
top cover (which is never glued). Be sure the sides of the stand don't protrude from the 
other segments, or you may have trouble inserting it into the case later. Let dry at least an 
hour. 

Glue the stand into the back of the case. If it doesn't fit, sand down any interference 
points. Let it dry. 

Prepare the hardboard for painting by sanding it all over with medium-grit sandpaper, 
smoothing imperfections and softening corners. Finish with fine-grit paper, then paint. For 
bright colors, it helps to start with a primer coat of white acrylic latex. Don't forget to sand 
and paint the front cover and top cover pieces. 



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The Autophenakistoscope 





• Cut all the wire segments and strip 
1/3" from both ends of each. You'll 
need: 

• 12" pieces (14): red (6), black 
(6), orange, brown 

• 6" pieces (5): blue, yellow, 
purple, green, white 

• The power wires are red and black, 
and the others are the signal wires. 
If you don't have enough colors, 
label the wires as you make the 
connections. 

• Solder leads to the two 5K pots, 
using 12" red and black segments 
for the outside terminals (for 
positive and negative power), and 
6" unique colors for the signal pins 
in the middle — I used purple for 
motor and yellow for strobe. The 
red and black should run in 
opposite directions on the 2 pots. 

• When soldering wires to 
posts, first make a 
mechanical connection by wrapping 
the wire around the post, then 
solder the connection. 




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The Autophenakistoscope 




Solder leads to the IR emitter, which is the dark one in the emitter/detector pair. Solder a 
black wire to the shorter (-) leg of the emitter, and a 100Q resistor connected out to a red 
wire to the longer (+) leg. Seal the connections with heat-shrink tubing by slipping pieces 
over and shrinking them with a heat gun or lighter. 

Solder leads to the IR sensor. Solder a red wire to the short leg and put a 10K resistor 
between the black wire and the long leg. Also connect a green sensor wire between the 
negative lead and the resistor. Seal with heat-shrink. 

Solder a white wire to the longer leg of the strobe LED and a black wire to the shorter leg. 



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The Autophenakistoscope 




Connect a red wire to one side of the toggle switch and a black wire to the other through 
the second 10K resistor. Connect a blue wire between the resistor and the switch. Solder 
the connections and seal with heat-shrink. 

Solder the 12" orange and brown wires to the motor terminals. 

Make 2 terminal blocks to organize all circuit connections to positive and negative voltage. 
Cut a 12-post terminal strip in half, and use markers to color one side red and the other 
black. For each half, connect a matching lead, and jumper all of the remaining terminals 
using bare wire. Use a multimeter to confirm that there's near-zero resistance between all 
terminals on each block. 



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The Autophenakistoscope 







Use two 2-56x 1 /4" or similar small screws to mount the motor to the stand and attach a 1/8" 
shaft collar to the motor shaft, spaced away from the motor a little so it doesn't hit the 
mounting screws when it rotates. Verify that the collar is tight and that the motor turns 
freely. 

Mount the IR emitter and sensor facing each other in the stand. I decided to put the emitter 
in back because it's always on and it connects only to the red/black terminal blocks. 

Mount the pots and switch onto the front panel using the included hardware. If necessary, 
trim the pot shafts to fit the knobs. Install the knobs, and clip any alignment tabs to enable 
the pots to sit flush against the panel. 



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The Autophenakistoscope 




• Use double-stick foam tape to mount the terminal strips to the floor of the case in back. 

• Assemble the Arduino and motor controller boards following the included instructions. On 
the motor controller, you can use the regular Motors header, but substitute the longer, 
stackable headers, sold separately, for the Encoder and Power headers. Finally, plug the 
motor controller board onto the Arduino, making sure to properly line up the pins. 

• Download the Autophenakistoscope source code from the documents section, then 
compile and upload to your Arduino. 





Make the following connections to 
the Arduino board: 

• Yellow/strobe pot: Analog pin 5 

• Purple/motor pot: Analog pin 

• Green/I R transistor: Digital pin 2 

• White/strobe LED: Digital pin 13 
(the LED hangs free, not 
mounted yet) 



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The Autophenakistoscope 



Step 10 




• Connections continued: 

• Brown and orange/motor: Shield 
motor B (upper 2 terminals on 
the Motors header) 

• Blue/mode switch: Digital pin 3 

• Red/positive terminal block: 5V 
Power 

• Black/negative terminal block: 
Ground 

• Run all the red/positive and 
black/negative leads through the 
wire channel and connect them to 
corresponding terminal strips. You 
can tidy up the wiring with small zip 
ties. 



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The Autophenakistoscope 



Step 11 — Final assembly and testing 




Cut holes in the center of the sync wheel and the 2 smaller cardboard disks to fit snugly 
over the motor shaft. Slip the middle-sized disk over the shaft, then the sync wheel (be 
careful not to bend it), and finally the smallest disk. 

Slip the CD onto the motor shaft, facing front. Fit it around the smallest cardboard disk, 
and secure it so it won't slip. I used another knob to hold it, but you can also use a shaft 
collar and washer. I drilled the knob to let the long shaft pass through, but you can also cut 
the shaft. 

It's time to run some tests. Connect power to the Arduino, and you should see the strobe 
flash and the motor spin up to about half power. The strobe should synchronize to the 
wheel; dim the lights and shine the LED on the image disk to check. Magic! 

If it behaves the opposite way (motor goes full speed when turned down low), reverse the 
Arduino connections for the 2 pots. If it doesn't work, double-check all your connections to 
the Arduino, and if you still have problems, see my troubleshooting guide at 
retrotronics.com/autophenakistoscope. 

Once your Autophenakistoscope works, close it up by mounting the white strobe LED to 
the front panel, gluing on the front panel, and slipping the cover on top. Phenakistastic! 



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The Autophenakistoscope 



Step 12 — Design your own image disks 




• To generate the sample image 
disks, I took some vintage 
animation loops and cleaned them 
up using GIMP software 
( http://gimp.org ). To make the 
process easier, I wrote a web 
application, http://www.retro- 
tronics.com/APKS/disk.p... , that 
you can use to make 'scope-ready 
disks from uploaded photos. 



Time and motion studies 

Just like the movies, the Autophenakistoscope works best in low light. Dim the lights and plug it 
in. It first spins up the motor to half power, flashes the LED a few times, then starts reading 
inputs from the potentiometers. When the motor pot is turned all the way down, the motor should 
be off. When the strobe pot is all the way down, it should flash about once per second (1Hz). 

Adjust the motor and the flash frequency to a moderate level. Toggle the mode switch once or 
twice to figure out which is which — in automatic mode, the image should stabilize; in manual 
mode, it will wander or not be legible. 

It's time to experiment. Adjust the knobs and you'll see that multiple frequency combinations can 
produce smooth moving images. It's also possible to freeze the image by adjusting the rotational 
frequency to match the strobe frequency. 

When I first built this project, I noticed that the image can "roll" just like it used to on the old 
black-and-white TV when I was a kid. It turns out that this is a completely analogous result. 

Another interesting experiment is to videotape the Autophenakistoscope. You'll find that the 
frequencies of the strobe can coincide with the scanning frequency of your recorder. If you get it 
just right, the scope will appear to be dark in your video when it looks well-lit to your eyes. 



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The Autophenakistoscope 
Mechanical television 

I discovered the phenakistoscope while investigating mechanical television. Mechanical 
television is actually very simple, but impractical except for very small screens. The scan lines 
are generated with a perforated spinning disk known as a Nipkow disk. 

In the 1920s, television started with 24- or 32-line screens, and there were regular mechanical 
television broadcasts decades before Milton Berle showed his face in our (grandparents') living 
rooms. 

A 420-line spinning disk is another story; it would have to spin at very high frequencies to fully 
paint the screen at a rate that would satisfy the eye. But the Autophenakistoscope would make a 
great platform for a modern, experimental mechanical television. I'd also like to see it scaled up. 

This project first appeared in MAKE Volume 20 . page 100. 

This document was last generated on 201 2-1 0-31 11 :28:44 AM. 



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